The present invention relates to a method of manufacturing an iron core of a multi-phase linear motor including a hybrid type linear motor, a VR (variable reluctance) type linear motor and a permanent magnet type linear motor.
FIG. 9 is a longitudinal sectional view illustrating a cylindrical linear motor relating to the present invention.
In FIG. 9, each the stator iron cores 101, 102, 103 and 104 of a stator 100 of the cylindrical linear motor includes an outer peripheral portion formed into a stepped ring which is thick in the thickness direction thereof and an inner peripheral portion on which a plurality of stator teeth 105 are disposed at an equal pitch in the shaft direction. The stator iron cores 101, 102, 103 and 104 are supported by a frame 116 and housed therein.
The stator iron cores 101 and 102 are combined so that the outer peripheral portions thereof abut against each other to form a ring groove in which a ring winding 106 is disposed and held between the stator iron cores 101 and 102. Similarly, a ring winding 107 is disposed in a ring groove formed between the stator iron cores 103 and 104 and is held between the stator iron cores 103 and 104.
In the cylindrical linear motor, the stator iron plates 101 and 102 and the ring winding 106 constitute one phase and the stator iron plates 103 and 104 and the ring winding 107 constitute another phase to thereby constitute two phases as a whole.
A ring permanent magnet 108 is held between the stator iron cores 101, 102 and 103, 104 constituting the two phases and is magnetized in the shaft direction of a mover 109.
A mover iron core 110 of the mover 109 is cylindrical and a plurality of mover teeth 111 are disposed on an outer peripheral surface of the mover iron core 110 at an equal pitch in the shaft direction. The mover 109 is supported movably in the shaft direction through bearings 114 and 115 by brackets 112 and 113.
The stator teeth 105 and the mover teeth 111 have the following positional relationship: when the stator teeth 105 disposed on the stator iron core 104 are just opposite to the mover teeth 111, the stator teeth 105 disposed on the stator iron core 103 are shifted by 2/4 of the tooth pitch in the shaft direction with respect to the stator iron core 104. Further, the stator teeth 105 disposed on the stator iron core 102 are shifted by 1/4 of the tooth pitch in the shaft direction with respect to the stator iron core 104. The stator teeth 105 disposed on the stator iron core 101 are shifted by 3/4 of the tooth pitch in the shaft direction as compared with the stator iron core 104.
With the above configuration, the cylindrical linear motor constitutes a two-phase hybrid type linear motor.
However, the cylindrical linear motor configuration above has a drawback in that a winding accommodation portion cannot be made larger and the ampere-conductors per phase cannot be increased. Consequently, the driving force is low. Further, there is a drawback in that since the stator iron cores 101 and 104 are positioned farther from the permanent magnet 108 than the stator iron cores 102 and 103, the magnetic circuit is not uniform and the driving force varies depending on the excitation phase. Furthermore, since the phases are disposed in the shaft direction theoretically, the length of the motor in the shaft direction is made longer. In addition, since the permanent magnet 108 is disposed on the side of the stator 100, a motor casing is required and at the same time the length of the mover 109 in the shaft direction is required to be made longer than the length of the stator 100 in the shaft direction. Accordingly, there is a drawback in that the inertia of the mover 109 is increased. At the same time, there is a drawback in that it is difficult for this arrangement to constitute a multi-phase linear motor.
Accordingly, the present inventors have already proposed a linear motor which solves the above drawbacks and have disclosed the following shape for a stator iron plate forming a stator iron core.
When k is a positive integer and m is the number of phases, the stator iron plate forming the stator iron includes 2km salient poles including m salient poles forming tooth tops of the stator teeth and m salient poles forming tooth bottoms of the stator teeth in the inner periphery of the stator iron plate, both of which are both arranged side-by-side to form one set and is configured to have k sets of salient poles (Japanese Patent Provisional Publication Nos. 6-189520 and 6-197517 or Nos. 189520/1994 and 197517/1994).
Further, when k is an integer equal to or larger than 1, m is the number of phases, and n is an integer which is smaller than or equal to m/2 and is a value nearest to m/2, the stator iron plate includes km salient poles including n salient poles having a smaller inner diameter and (m-n) salient poles having a larger inner diameter at the tip of the salient poles opposite to the mover, both of as viewed from the mover which are arranged side-by-side to form one set and is configured to have k sets of salient poles (Japanese Patent Application No. 5-100810 or No. 100810/1993).
However, the linear motor configured as indicated above has the following problems.
(1) Since the teeth of the stator iron core or the mover iron core are formed by laminating the iron plates including the salient poles constituting the tooth tops and the salient poles constituting the tooth bottoms which are disposed in the predetermined relationship while rotating the iron plates by a predetermined angle, the salient poles must be disposed at an equal pitch in the circumferential direction and the motor cannot be formed into a flat plate or a semicircle.
(2) The external shape of the stator iron plate is also required to be the same when laminated and rotated and accordingly the external shape of the stator iron plate cannot be formed into a square in the case of a five-phase motor, for example.